Prediction of Maternal and Fetal Doravirine Exposure by Integrating Physiologically Based Pharmacokinetic Modeling and Human Placenta Perfusion Experiments

Ideal Time to Conduct a Pharmacokinetic Investigation After Delivery to Fully Capture the Effect of Pregnancy on Drug Exposure

Background

The World Health Organization is pushing to accelerate the study of new human immunodeficiency virus drugs in pregnant women. However, regulatory guidelines do not specify when to conduct pharmacokinetic studies in postpartum women. This knowledge gap carries the potential to jeopardize the outcomes and conclusions of clinical trials aiming to study the effect of pregnancy on drug exposure. We used physiologically based pharmacokinetic (PBPK) modeling along with clinical data to determine the time needed after delivery for drug exposure to return to prepregnancy levels.

Methods

A literature review was conducted to collect physiological parameters of pregnant and postpartum women. Regression analyses were performed to derive equations describing the parameters trajectory throughout pregnancy and post partum to inform our PBPK model. Published pharmacokinetic data in pregnant and postpartum women were used for the model verification. The PBPK model was subsequently applied to investigate pharmacokinetic changes throughout pregnancy and post partum.

Results

In agreement with the clinical data the PBPK model was able to describe the different effects of pregnancy on drug exposure, with bictegravir showing the largest reduction in exposure (approximately 50%) during the third trimester while ritonavir and raltegravir showing the lowest (approximately 30%). The successfully verified PBPK model predicted that all evaluated antiretrovirals mostly return to prepregnancy exposure 4 weeks after delivery.

Conclusions

Pharmacokinetic investigations on hepatically cleared drugs should not be conducted before the fifth week after delivery to fully characterize the effect of pregnancy on drug exposure. Because physiological changes remain after delivery, early measurements can underestimate the pregnancy effect on pharmacokinetics, leading to suboptimal dosing recommendations during pregnancy.

Physiologically-based pharmacokinetic models to predict drug exposure during pregnancy

As pregnant women are constantly exposed to drugs during pregnancy, either to treat long-term conditions or acute illnesses, drug safety is a major concern for the fetus and the mother. Clinical trials are rarely made in this population due to strict regulation and ethical reasons. However, drug pharmacokinetic (PK) parameters vary during pregnancy with an increase in distribution volume, renal clearance and more. In addition, the fetal distribution should be evaluated with the importance of placental diffusion, both active and passive. Therefore, there is a recent interest in the use of physiologically-based pharmacokinetic (PBPK) modeling to characterize these changes and complete the sparse data available on drug PK during pregnancy. Indeed, PBPK models integrate drug physicochemical and physiological parameters corresponding to each compartment of the body to estimate drug concentrations. This review establishes an overview on the current use of PBPK models in drug dosage determination for the pregnant woman, fetal exposure and drug interactions in the fetal compartment.

The impact of obesity on doravirine exposure in people with HIV

Obesity incidence is increasing among people with HIV. Doravirine is a recommended first-line antiretroviral drug in many countries with no data from people with obesity. This study investigates the exposure of doravirine 100 mg standard dose in obese versus normal weight patients using clinical data combined with physiologically based pharmacokinetic modelling. Results from both approaches showed an elevated doravirine exposure during obesity, yet within the safety range of doravirine with no need for dose modification.

A physiologically based toxicokinetic model of P-glycoprotein transporter-mediated placenta perfusion of dexamethasone in the pregnant rat

The present dosage of Dexamethasone (DEX) administered to pregnant women may pose a risk of toxicity to their unborn offspring. We aimed to develop a maternal-fetal physiologically based toxicokinetic (PBTK) model for DEX in pregnant rats, with a specific focus on the role of the P-glycoprotein (P-gp) transporter in placenta perfusion, and finally facilitate the optimization of clinical DEX dosage. We conducted animal experiments to determine DEX concentrations in various rat tissues, and constructed the PBTK model using MATLAB software. Sensitivity analysis was performed to assess input parameters and the model stability, with fold error (FE) values serving as evaluation indices. Our results indicate the successful construction of the PBTK model, with the fitting key parameters such as the absorption rate constant (Ka), intrinsic hepatic clearance (CLh,int) and intrinsic P-gp clearance (CLint,P-gp). The median concentration of DEX in maternal plasma, fetal plasma, fetal lung, and fetal brain were determined, which allowed us to fit the tissue-to-plasma partition coefficients for the fetal lung (Kp,lung,f) and fetal brain (Kp,brain,f). After making adjustments, all calculated FE values were found to be less than 2, demonstrating the acceptability and accuracy of our model's predictions. Our model integrated external literature data and internal animal experimentation to comprehensively evaluate the maternal-fetal PK characteristics of DEX. These findings provide valuable support for the optimization of clinical DEX dosing.

Drug exposure during pregnancy: Current understanding and approaches to measure maternal-fetal drug exposure

Prescription drug use is prevalent during pregnancy, yet there is limited knowledge about maternal-fetal safety and efficacy of this drug use because pregnant individuals have historically been excluded from clinical trials. Underrepresentation has resulted in a lack of data available to estimate or predict fetal drug exposure. Approaches to study fetal drug pharmacology are limited and must be evaluated for feasibility and accuracy. Anatomic and physiological changes throughout pregnancy fluctuate based on gestational age and can affect drug pharmacokinetics (PK) for both mother and fetus. Drug concentrations have been studied throughout different stages of gestation and at or following delivery in tissue and fluid biospecimens. Sampling amniotic fluid, umbilical cord blood, placental tissue, meconium, umbilical cord tissue, and neonatal hair present surrogate options to quantify and characterize fetal drug exposure. These sampling methods can be applied to all therapeutics including small molecule drugs, large molecule drugs, conjugated nanoparticles, and chemical exposures. Alternative approaches to determine PK have been explored, including physiologically based PK modeling, in vitro methods, and traditional animal models. These alternative approaches along with convenience sampling of tissue or fluid biospecimens can address challenges in studying maternal-fetal pharmacology. In this narrative review, we 1) present an overview of the current understanding of maternal-fetal drug exposure; 2) discuss biospecimen-guided sampling design and methods for measuring fetal drug concentrations throughout gestation; and 3) propose methods for advancing pharmacology research in the maternal-fetal population.

Antiretrovirals for Human Immunodeficiency Virus Treatment and Prevention in Pregnancy

Safe and effective antiretroviral medications are needed during pregnancy to reduce maternal morbidity and mortality associated with untreated human immunodeficiency virus (HIV) infection and to prevent viral transmission to the infant. Pharmacokinetic studies have helped inform the appropriate dosing of antiretroviral medications during pregnancy. However, data from these studies consistently become available years after initial regulatory approvals in nonpregnant adults. In this article, the authors provide an overview of considerations in use of antiretroviral medications in pregnant people with or at risk for HIV, pharmacokinetic studies that helped support recommended options, and therapies either under active investigation or in need of prospective study.